Secondary electron suppressor



Jan. 8, 1957 c. H. GLEASON 2,777,085

SECONDARY ELECTRON SUPPRESSOR Filed May 29, 1952 l I W 'IIIIIIIIIIIIIIl/III)HIIIIII T M v I I a INVENTOR C N. 61.57750 ATTORNEY United States Patent Office 2,777,085 Patented Jan. 8, 1957 SECONDARY ELECTRON SUPPRESSOR Charles Herbert Gleason, Bloomfield, N. L, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 29, 1952, Serial No. 290,628

3 Claims. 01. 313-406) This invention relates to a secondary electron inhibitor, and while possessing utility with various electron discharge devices, it is intended for and has very marked advantage for use with resnatrons.

A resnatron is a beam tetrode cavity resonator electron discharge device intended for very high power continuous output of ultra-high frequency. Feed-back from a resonator maintains oscillation which obtains bunching of beamed electrons by varying the potential between the control grid and cathode. A screen grid or tetrode speeds up the beamed and bunched electrons which therefore have high velocity when striking the anode or collector. High velocity electrons striking a surface cause secondary electrons to break away from surface and absorb energy from the resonant system. The secondary electrons are low velocity and take a reverse path to the primary electrons and are adverse to any useful purpose.

The primary object of the present invention is to squelch the secondary electrons.

Otherwise expressed, the invention contemplates means for deterring entry of secondary electrons into the resonant system of the device.

A further object of the invention is to avoid applying suppressing influence to the secondary electrons which will adversely affect attainment of energy transfer from the primary electrons to the resonant system.

Other objects of the invention will appear to those skilled in the art to which it appertains as the description proceed-s, both by direct recitation thereof and by implication from the context.

Referring to the accompanying drawing, in which like numerals of reference indicate similar parts throughout the several views:

Figure l is a sectional elevation of a resnatron embodying my invention;

Figure 2 is a cross section on line II-II of Fig. 1; and

Figure 3 is a somewhat diagrammatic cross section of a modified construe-tion.

In the specific embodiment of the invention, shown in the drawing in an arbitrarily selected resnatron, the general organization provides one hollow body resonator, herein designated cathode resonator 10, coaxially within a second resonator, herein designated anode resonator 11. It is a known fact that the voltage distribution of such resonators is at maximum at the mid cross section, and it is there that greatest power can be derived from a traversing electron beam. The illustrated resnatron therefore provides a cathode 12, comprising a circular series of emitting filaments, coaxially within the resonators substantially midway of their longitudinal dimensions, and shows the cathode resonator correspondingly slotted opposite the cathode filaments, thereby constituting that section of the resonator wall a control grid 13 and affording clear passage for radially directed beams of electrons from the cathode. The mid-section of the inner cylindrical wall 14 of the anode resonator is cut away at its mid-section to also permit passage of the electrons from the cathode. Longitudinal grid strands 15 span the cut-away section of the said wall 14 and are arranged to have registration radially with the strands of the control grid. The circular series of said strands 15 constitutes an accelerator grid.

The outer cylindrical wall of the anode resonator 11 provides an anode 1 at the mid-section thereof opposite the cathode so that electrons emitted radially from the cathode and passing between the grid strands will have straight line approach to the anode. For convenience in fabrication, the anode may be constructed as an inwardly directed circumferential channel with peripheral wall 17 and inwardly directed flanges 18. Said flanges are shown as flaring somewhat and as integral with a re-entrant section 19 of the resonator wall. The interaction space is the annular region from the accelerator grid 15 radially outward to a cylindrical surface defined by the inner edges of the anode flanges, and it is an essential purpose of the present invention to suppress secondary electrons emitted from the anode so they do not get into this interaction space, but remain in the hollow 20 between said flanges.

According to the showing in Figs. 1 and 2, a magnet 21 is provided with its poles at the outside of and next said flanges 18, the magnet poles being directed toward each other so that the magnetic flux is transverse to the electron beam and at the part of the beam substantially beyond the aforementioned interaction space through which the beam first passes before reaching the imposed magnetic field. The primary electrons in the beam are accelerated by accelerator grid 15 and therefore have high velocity when entering the anode hollow 20 between said flanges. The magnetic field introduced by magnet 21 consequently has little opportunity to affect the high velocity electrons which therefore continue in substantially straight paths to impingement upon the anode. High velocity electrons will dislodge secondary electrons from a surface struck thereby even where the surface is one not intended to be emissive of secondary electrons. In other words, any metal capable of functioning as an anode, will unavoidably emit some secondary electrons when struck by high velocity primary electrons. The secondary electrons are, however, of low velocity character and therefore, being emitted in a magnetic field, will be deflected or caused to spiral, and in most instances will thereby be influenced to remain in the anode hollow and return to the anode surface. Thus the secondary electrons are squelched and do not get out into the interaction space where they would absorb rather than supply energy to the output system. The resnatron consequently develops a much greater output than prior art constructions not having the magnetic control of the present invention.

In order that the magnet may be applied within the reentrant section 19 of the resonator wall, said magnet may be made in two halves with a diametric split 22. Other constructions and arrangements of magnets may be utilized to accomplish the purpose. Furthermore, since the primary electrons are directed as radial beams between the grid strands, the anode may be constructed with individual hollows for each beam and individual magnets for each hollow.

The suggested alternative structure above-mentioned is illustrated in Figure 3 wherein anode 16a is shown with hollows or pockets 20a opposite each filament of cathode 12. Straight line passage for the electron beam is provided as before by placement of the grid strands to the side of such path. Individual magnets 21a are shown for each hollow or pocket 20a.

I claim:

1. A resnatron having a cathode and coaxial cathode and anode resonators one within the other and having electron beam path openings intermediate of the ends of the resonators, said resonators providing a reaction space in the region of said openings, a hollow anode opposite 3 said openings in opposition to said cathode and on a straight line path of an electron beam emitted from said cathode and directed through said openings, and a magnet beyond said reaction space and next to said hollow anode with the poles of the magnet on a line transverse to the straight line path of the electron beam.

2. A resnatron in accordance with claim 1, wherein said hollow anode comprises a circumferential channel having a peripheral wall and flanges projecting inwardly toward the axis from said peripheral wall and flaring from each other in approach toward said axis.

3. A resnatron in accordance With claim 1, wherein said hollow anode comprises a circumferential channel having a peripheral wall and flanges projecting inwardly toward the axis from said peripheral wall and flaring 4 from each other in approach toward said axis, and whercin the poles of said magnet conform to and are in close proximity to the outside surfaces of said flanges.

References Cited in the file of this patent UNITED STATES PATENTS 2,298,949 Litton Oct. 13, 1942 2,410,054 Frcrnlin Oct. 29, 1946 2,451,987 Sloan Oct. 17, 1948 2,459,593 Sloan Jan. 18, 1949 2,477,633 Litton Aug. 2, 1949 2,557,700 Sloan June 19, 1951 2,591,997 Backmark Apr. 8, 1952 2,632,866 McArthur Mar. 24, 1953 2,662,980 Schwede Dec. 15, 1953 

